Metallurgical furnace



Feb. 5, 1946.

A H. J. NESS METALLURGICAL FURNACE 1942 4 Sheets-Sheet 2 Filed Aug. 22y

1, 1 059 7 1w, 7/ /Z 4a 1 m 1w 1 M 11, 1, a 1 .1 Ww 7 v1 Ww 11l 7 au j 1. W/ M 1 1 u 1 ,o J1 1 INVENTOR I Ia'roZdJZVess H. J. NESS 2,394,002r

METALLURGICAL FURNACE Filed Aug. 22, 1942 4 Sheets-Sheet 3 Fa. s, 194s.,

` Feb. vEi, 1946. H. J. NESSI I METALLURGICAL FURNACE 4 sheets-shea 4 Filed Aug. :22, 1942 INVETOR D v flraZzZJ/ss WMWW.

ATTORNEY f Patented Feb. 5,1946

- UNITED STATE y t v2,394,002

METALLURGICAL FURNACE Harold J .'Ness, Nutley, N. J., assignor to Metallurgical Processes Co., a partnership consisting of Harold J. Ness and Martin A. Ness, both of Nutley, and Alfred Rg Becker and Marvin J. Reynolds, both of Montclair, N. J.

Application August 22, 1942, Serial No. 455,720

zroiaims.

This invention relates to lfurnaces and more' particularly to a method of and means for Pro..

ducing furnace atmospheres suitable for theheat treating of metals and other lmaterials which are liable to contamination by the usual furnace atmospheres, or for the carburization of iron and steel.

In the usual furnace atmospheres it is not possible to heat treat metals, such as iron and steel,

without considerable oxidation and decarburization thereof. The carbon dioxide, water vapor or any free oxygen inthe furnace act to scale or oxidize the metal, and the hydrogen and nitrogen in the presence of traces ofoxygen or water vapor, are strong decarburizing agents.

Heretofore, in the operation of heat treating atmosphere furnaces efforts have been made to prevent oxidation and decarburization by regulating the ratios between the various ingredients of the furnace atmosphere. Stansel and Dantsizen in the General Electric Review for March and May, 1939, have shown, however, that the ratio Abetween the various components of a furnace atmosphere which will not scale are radically diiferent from the ratios required in order to prevent carburization or decarburization of steel. It, therefore, has not been possible to prevent both oxidation and decarburization or carburization of the treated metal merely by adjustment of the ratios of the reducing gases, such as carbon monoxide, hydrogen and methane, to the oxidizing gases, such as carbon dioxide and water vapor. The present invention is concerned with the elimination of these difliculties and in obtaining a furnace atmosphere for the heat treating of metals in which all three of these detrimental actions are eliminated. This is accomplished by introducing an additional component into the furnacel atmosphere, namely, lithium or a compound of lithium, which overcomes the tendency of the heat treating atmosphere to either effect oxidation, carburization or decarburization of the metals being heated and which therefore, renders it unnecessary to effect 4.5

a balance between vthe variousI components resulting from combustion of the gases.

In my prorPatent No. 2,181,093,y granted `No vemb'er 21, 1939, there is described one method of producinga lithium containing atmosphere in a furnace in which various metals may be heated in the presence of Iordinaryrombustion gases without detrimental oxidation or decarburization. In accordance with` the disclosure of that patent, a compound of lithium, such as the carbonate, is introducedfinto th furnace ,atmosphere in powdered form. Inorde'r torobtain a uniform flow of the compoundin minute quantities, the compound is atomized by agitation and by passing air orother gas therethrough to produce a suspension of the compound-in lthe gas. AThe required quantity ofthe compound `laden gas may then be introduced into the furnace mixed with the air or fuel or independently thereof. It is believed that in the lheat of the furnace the lithium compound or a portion thereof -is reduced to lithium oxide which vreacts withthe 4carbon monoxide present in the furnace gasesto liberate lithium metal in accordance with the-following equation: -1 f is then repeated with the lithium oxide so formed.

In my copending application Serial No. 384,641, filed March 22, 1941, now Patent No. 2,346,698, granted April 18, 1944, and entitled Controlled atmosphere furnace, of which the present application is a continuation in part, there is disclosed a method of and apparatus for introducing lithium or lithium, compounds into a furnace for accomplishing the' purpose of ,the aforesaid patent. In accordance with the disclosure of said application, the lithium, or a compound or mixtures of compounds thereof, is vaporized and introduced into the treating chamber of the lurnace by means of a carrier gas. This carrier gas may be a non-oxidizingr medium,such as nitrogen, or hydrogen, although a gas resulting from the combustion of a liquid or gaseous fuel is preferred. Air may also beemployed as a carrier gas, if desired.

The amount of lithium required for conditioning the atmosphere of the ffurnace in the manner described in said later application is ex. tremely small; for instance, a muilie furnace heated to about 1400 F. and having a volume of approximately two thousand cubic inches and a gas ow of approximatelylone hundred cubic feet o per hour, may be completely conditioned for a period of fifteen hours or more with six ounces of a lithium compound mixture composed of 40% lithium chloride and .lithium carbonate.

u The present invention is an improvement upon y the invention of said application, one oi the ob'-,

jects thereof being to still 4further reduce the amount of lithium compound required to condiv Sain Tour in a paper entitled Water vapor in paratus ,is of no advantage since, accordingto furnace atmospheres," published in the Transactions of the American 'Society for Metals for 1941, at page 710, in the reheating of the'gases to the treating temperature, water vapor may f againbe formed in amounts of from 3 to 5% or may be employed interchangeably for both heat treating of metals or for carburization of iron or steel.

A 'further object is to provide a furnace atmosphere in which bright or clean carburizing may be eiectedand further in `which such carburizing may be accomplished at relatively low temperatures and at higher rates of penetration than has been obtained in prior art methods.`

A still further object is to effect an economy in the use of the carburizing gas. Still another object is to provide a completely dry atmosphere in 4the furnace throughout the entire heating chamber and during all c ondi.

A still further object is to provide a novel furnace construction in which the foregoing objects may be accomplished.

.tions of operation thereof.

Other objects and advantages will hereinafter The detrimental eilects of water vapor in the furnace atmosphere has been long appreciated and extreme precautions vhave been taken in an effort to prevent its introduction into the furv nace. For thisv purposel involved refrigerating and dehydrating apparatus has been provided in order to reduce the moisture content in the products of combustion to a negligible degree. HOW- ever, such methods have 'not been effective to produce a dry atmosphere in the furnace since in the reheating of the gases to the furnace temperature, water vapor is again formed. The introduction of lithium or its compounds. into the furnace atmosphere, as set forth in the aforesaid applications, overcomes or neutralizes the detrimental effects of water vapor in the furnace atmosphere or acts to prevent its formation, so that the provision of drying apparatus is unnecessary.

, However, applicanthas discovered that improved operation of the furnace may be obtained by the elimination of a portion of the water vapor from the treating gases prior to thel introduction thereof into the heating chamber, this improvement. residing primarily in the ability to produce the non-oxidizing and non-decarburizing heat treating-atmosphere or the desired carburizing atmosphere with a reduced quantity of lithium compound; in producing the requisite amount of lithium in" the atmosphere atvlower temperatures; in the maintenance of suchvprotective at mosphere at materially lower heat treating or carburizng temperatures; and in an improvement ixr the surface condition of the Itreated metals.

In accordance with the present invention the air and fuelmi'xture may be burned in the usual manner or they may be cracked by externally applied 'heat without combustion, either operation producing an increase in the moisture conv tent above that ofthe original mixture. The

more.- The condensed waterrvapor is then removed from the cooled gases and the vapor produced from heating of a lithium compound is introduced into the gas. The gases are then reheated and introduced in the heating chamber of the furnace. The formation of water vapor ordinarily incident to the reheating of the gases is. either inhibited or its effectiveness neutralized by the presence of thelithium in the atmosphere.. The partial removal of the water vapor greatly reduces the work which the lithiumis required to do and therefore, enables .the atmos-l phere to be conditoned with a lesser amount of lithium. For instance, a furnace of the muiile type ordinarily requiring the consumption of six .ounces of 'lithiumcompounds overa period of fteen hours for the conditioning of the furnace,

when no drying is employed, may, with the removal .of a portion of .the water vapor, be conditioned with an equal amount of the same compound for a period Iof approximately sixty hours. Moreover, whereas it required a temperature of about 1750 F. to generate the required amount .y

of lithium to condition the atmosphere without the removal of water vapor, a sufficient quantity to effect the desired result may be produced at a temperature of about 1400 F. after removal of the aforesaid portion ofthe water vapor. 'I'he activity of thev lithium in the furnace atmoscracked or burned gases are then 4partially dehydrated by cooling, Preferably to a temperature' of from 50 to 100 degrees F. Further cooling of thetgases or, the use-:lof supplemental drying apphere is dependent to some extent upon the temperature existing in the furnace, but when the water vapor is reduced by the precooling of the gases, .the amount of lithium required to neutralize its effect is so smallthat sufficient activity is obtained at much lower temperatures than would lotherwise be possible and a satisfactorily conditionedheat treating atmosphere may be created and maintained at temperatures as low as 600 F. Another very important advantage in the use of extremely small quantities of lithium in the treating atmosphere is the absolutely clean and bright surface of the treated parts on their removal from the furnace. This bright surface is obtained both when` using a non-carburlzing atmosphere'as in annealing, hardening, tempering, etc., and when using a carburizing mixture in the furnace. As will hereinafter appear, and as pointed out in Patent No. 2,240,146, entitled Carburizing ferrous metals. while lithium is effective to prevent carburization in ordinary heat treating atmospheres, it acts in the presence of a carburizing gas mixture `to accelerate carburization, and to enable carburization to be carried out at much lower temperatures than heretofore hasl been possible in gasy carburizing processes.

'I'he invention will best be understood by reference to the accompanying drawings, in which: Fig, 1 is a vertical sectional view of an atmosphere furnace embodying the present invention;V`

Fig. 2 is a sectional view of the gas generating chamber taken on the line 2-2 of Fig. l:

Figs. 3, 4, 5, and 6 aresectional views. of the carriergas generating chamber'taken on the lines 3 3; 4 4: 5-5;.and 6 0, respectively, of Fig. 2;

Fig. 7- is a sectional view of a gas and air mixing device for supplying .avregulated mixture thereof to the carrier gas generating chamber; Fig. 8 is a sectional view taken on the line .-3 of Fig. 1;

Fig. 9 is a vertical sectional view of a modified form of muiile, Work conveying belt, and quenching chute;

Fig. 10 is a view on the line Il--Il of Fig. 9; Fig. 11 is a. vertical sectional view of the quenching tank, taken on the line II-I I` of Fig.

9; and l0 Fig. 12 is a schematic view of a timing mechanism andeircuits controlled thereby for predetermining the operation of air and gas inlet valves for supplying, alternately, a carburzing and a heat treating atmosphere to the furnace. l5

Referring first to Fig. 1, the furnace there shown comprises a muille Il of rectangular cross section composed preferably of a heat resisting meta-1 such as nickel or nickel-chromium alloy.

lSince the interior of the munie is continuously 2o provided with a protective or non-oxidizing atmosphere, the munie may be composed of an iron or steel inner lining, preferably welded at one end to the nickel or nickel-chromium alloy jacket, or it may be composed entirely of copper plated iron or steel. The mume I0 extends, at the forward end, through a rectangular opening I I in the refractory combustion chamber I2. The rear of the muille is shown terminating within an opening I3 in the rear wall of the refractory com- 30 bustion chamber I2, The forward end of the muiile is provided with a'ilange I4 to which is secured a mullle extension I5 provided with a suitable door I5 at its outer end. The door may bev controlled by means of a foot pedal II con--35 nected' thereto through a flexible cable I8 passing over suitable pulleys I9 and 2l. 'Ihe pedal II is pivoted at 22 and is adapted to be held in any suitable raised position by means of a latch 23 thereon engaging in suitable notches in the ser- 4o rated plate 24. 4Extending downwardly from the muiile extension I5 is a quenching chute 25 which terminates beneath the body of a quenching medium 26 contained within a suitable receptacle The mullle I0 is heated by two series of burners 28 extending into the combustion chamber I2 at opposite sides thereof beneath the mume Il. The burners 28 are supplied with a. combustible mixture of air and gas by conduits 2Q; The com- 50 bustion chamber I2 is vented by a plurality of pipes 31 extending form a point just above the center of the munie I3 through the refractory insulation and terminating above the furnace shell. This location of the vents allows lthe oom- 55 bustion gases passing up about the sides of the muiiie, to sweep over the top thereof, and results in an extremely uniform heating of the muile.

Situated to the rear of the combustion chamber is a vaporizing chamber-33 and a gas generate0 ing chamber 39. The vaporizing chamber 33 is provided. with burners 23' supplied with a combustible mixture of gas and air by conduits 25', and is ventedby ports 31'. The airandgaslines and 3|, respectively, are each provided with I6 two branches. those in the air line having electrically controlled valves 32 and 32' therein, respectively, by which air under suitable pressure is supplied to a pair of Venturi mixing tubes 35 and 35' connected to the manifolds associated 10 with the burners and 23', respectively. The two branches ofthegaslinell areprovldedwith pressure regulating valves 36 and 35?. the outlet sides of whichareconnectedtothethruatsof the Venturi tubes 3l and 3l', respectively..

The electric valves 32 and 32' are operated under the control of thermocouplee located in the combustion chambers I2 and 33, respectively, only the couple 33 associated with the chamber I2 being shown. This comprises a disc 34 of heat resisting and good heat conducting material, such as nickel or nickel-chromium alloy, disposed in a well or pocket formed in the top wall of the muille, and having the junction of the thermocouple welded thereto. l

The gas generating chamber is a substantially rectangular combustion chamber contained within a mass of refractory heat insulating material- It is provided with suitable burners ll and vents 4L chamber 35 is a U- shaped cracking unit 42, also shown in Fig. 2. An air and gas'mixture is introduced through the conduit 43 into one arm of the -U-shaped cracking chamber and is withdrawn therefrom through the opposite arm by way of the conduit 44.

The inlet conduit 43 extends laterally into the combustion chamber 3! beneath one leg 45 of the cracking chamber 42, entering the latter at the rounded end thereof. vThe outlet conduit 44 is connected to the other leg 45 of the cracking chamber and extends laterally therebeneath- Within the cracking chamber the inlet conduit 43 is provided with a perforated head or nozzle 41 which serves to break up and mix the incoming gas and to cause a lmiform distribution thereof within the space formed in the inlet end of the cracking chamber. Disposed within the legs 45 and 45 of the chamber 42 are a series of refractory baille members 4I to 53 spaced by flat refractory spacers .54. The baille members are variously shaped to effect a breaking up and slowing down of the gas and to cause a devious course. of travel thereof, whereby coring of the gas is prevented and a scouring action of the gas, overa large area of 'contact with the walls of the chamber andthe refractories therein, is obtained. In the embodiment shown, the refractory 43 is provided with a large number of small openings to distribute and retard the gas; refractory 45 is provided with marginal openings 55 to force the'gas to the side walls of the chamber; refrac- `toryhasacentralaperture5'Itocausea changeindirectinnofthegasandacrmngof the streams; and refractories 5|, 52 and 53 have a side, central, and side openings, respectively, to

continue this side-to-center and center-to-side movement, as indicated by the varrows in Fig. 2

' of the Obviously, other arrangements 15 beprovideiasforinstanceaneiectricvalve 6I in the air line 34. controlled bya suitable therm couple in the chamber 39, and in turn controlling the amount of gas drawn through the venturi e2, from the gas line 3l, the latter of which is provided with a gas pressure regulating valve 6I. i

The inlet and outlet conduits 43 and 44, ex-

tending as they do throughout the length of the lcombustion chamber la, provide additional time for the cracking of the gases and additional hot surfaces for contact with the gases. By terminating these conduits exteriorly of the furnace in T-connections e4, provided with closure plugs 65, they are readily accessible for the removal of any sediment or condensation productsl which may accumulate therein. The chamber 4 2 is closed by a refractory end member 88 clamped between metal plates 61. 68 whereby access is readily had to the interior of the cracking chamber for removal of solid material deposited therein or for renewal or repair of the refractory inserts. This ability to readily clean the cracking chamber and the inlet and outlet conduits is extremely important as the cracking process, particularly with carburizing mixtures and with some grades of carbonaceous4 gas, produces heavy residues, which in time would interfere both with the free passage of gas therethrough and the proper heat exchange. y

Butane, propane, natural gas or other hydrocarbon gases, mixed with a suitable proportion of air, may be supplied to the cracking chamber, the ratio of the hydrocarbon gas to air depending upon the analysis of the former and the purpose for which the furnace is to be used. For the heat vtreating of metals, where a neutral atmosphare is desired, I prefer to employ a'ratio of approximately 1 part of propane to 18 parts of air, whereas for carburizing, a ratio of 1 part of propane to from 5 to 10 parts of air, depending upon the analysis of the gas employed and the type, analysis and quality of the carburized case desired, has proven highly satisfactory. In Fig..

1 the arrangement of valves, conduits, etc., for obtaining the requisite gas and air mixture has been shown diagrammatically. Hydrocarbon gas from any suitable source is provided through a conduit 69 provided with a zero 'governor 10 to maintain atmospheric pressure therein. The conduit 69 is provided with three branches 1I, l2, 13, each having an electric valve 14a, 14h and '|4c, respectively, therein whereby the gas may be .permitted to flow through any one or more of contact, the windings of the valves 14a and 14a will'be energized, causingthe same to be opened, whereas the remaining valves 14h and 1.4, and

`, 14h and 'lic will normally be-clod so that the air and lgassupplied to the cracking chamber will be determined only by the valves Maand 16a. The ratio of air and gas supplied through these valves is determined by suitable orices in the branch 1 I. Referring to Fig. 7, these orifices are shown in discs 83 and 84, in the gas and air lines, respectively, .and are so proportioned as to produce a andai: ratio of approximately 1 s,so4,oo2

to 1a. consequently. when die' switch u a on a second contact, such a mixture will be supplied to the cracking chamber and will result in the provision of a neutral gas atmosphere in the mume i l, as will hereinafter appear.

With' the switch 8| on its third contact, the

windings of the valves 14h and leb will be energlzed, the others remaining deenergized so that only the former will be opened to enable the gas and air mixtureto be supplied through the branch 12. The orifices in this branch are so proportioned as to produce a gas and air. mixture of approximately 1'to 6.5 to be supplied to the cracking chamber. This mixture results in a carburizing gas being supplied to the munle'capable of producing a case of from 0.9 to 1.0% carbon. vThe valves 14e and 16o are controlled through the fourth contact of switch 8|. The orifices in the branch 13 are preferably so proportioned as to produce a gas and air ratio ofi to 8. This ratio will effecta case of from 0.7 to 0.8% carbon.-

. Additional branches and valves may be provided to supply other ratlos of gas and air in order to eiiect other degrees of carburization. For in-4k stance, an intermediate ratio of one part air to 7 parts gas will effect a case of from 0.8 to 0.9%. It will be understood that the exact ratio for any particular case will depend upon the analysis of the gas employed. It is, however, independent' of the time of carburizing. Increasing the time of treatment increases the depth of case but does not materially affect the concentration of combined carbon in the case.

In Fig. 1 the switch 8| has been shown as manually operable to provide either a heat treating or a carburizing atmosphere, but it will be understood that, if desired, it may be automatically controlled by suitable arrangements so that the atmosphere may be changed from carburizing to heat treating at any predetermined intervals. For instance, in carburizing of steel it is often desirable, after a predetermined carburizing period, to permit the work to soak in a neutral atmosphere for a further period in order to enable thecarbides to penetrate and diffuse into the' metal; and thereafter to repeat this cycle of carburization and diiusion one or more times. Such an arrangement will be described hereinafter, in connection with Flg.'12.

The air and gas mixture, whatever its proportion in passing through the chamber 42, is heated to the cracking temperature, preferablyv between 1800I to 1900* F., and the from the cracking chamber through the conduit 44 into a condensing chamber 81, (Fig/1). This condenser comprises a water Jacketed shell of substantially rectangular shape having a plurality of transversely extending hollow baiiles 84 proiecting alternately from opposite sides thereof and in communication with. the water Jacket whereby water from a suitable source 44 may be circulated through the jacket-'and through theinterior of the bailes. 'I'he water is 'conducted from the Jacket through a suitable outlet conduit 44. 'I'he 'cracked gas passes from conduit 44 into the condenser at the upper end thereof and circulates in a tortuous path around the baiiles Il and out of the condenser at the base threeof through a conduit si. The upper surfaces of the bailles 4I `are downwardly inclined towards the free ends thereof to enable the water, which is condensed from 'the cracked gas during the cooling thereof, to flow to the base of the condenser where itis removed by a suitable trap cracked gas is directed .conducted into the mulile 32 at the point where the gases leave the condensing chamber.

To permit cleaning of the condenser, one side wall thereof is secured by suitable bolts or screws to a 'nange 93 formed about the casing of the condenser.

The cooled and partially dried gases are conducted by means of the conduit 8| into a lithium compound generating chamber 06. The chamber comprises a metal pot 91 dependinginto the combustion' chamber 38 from a heat resisting alloy plate 08 which forms the top wall of the chamber`30. The plate 38 is supported by hanger rods 09, also of heat resisting alloy', from angle irons |00 extending transversely of the furnace. The pot 01 is spaced above the bottom wall of the chamber 38 to permit gas circulation therebeneath and to permit downward expansion of the pot as it is brought up to temperature. The chamber 30 is provided, as stated, with a pair of burners 28' to which a combustible air and gas mixture is supplied. The pot 31 is provided with a close fitting cover |03 from which a partition plate |04 is suspended. The partition plate has an opening |05 therein in substantial alignment with the gas inlet'conduit 0| and with the gas outlet conduit |00 by which the gases are I0. The pot 81 has an annular shoulder or seat |01 adjacent its lower end and supported thereon is a flanged cup. |08 adapted to contain a lithium compound or a mixture of lithium compounds. The burners 28 are adjusted by a suitable pyrometer control as stated, so as to maintain the lithium compounds at a suitable temperature to produce substantial vaporization thereof. The carrier gases entering the pot 31 are deflected in'part by the partitionplate |04 so as to pass overthe surface of themolten compounds whereby to entrain a portion of the vaporized material. The

amountof gas deflected by the plate |04 may be regulated by the size of the opening |05.

'I'he parts to be heated may be placed directly |2|, at its upper end above the piston H0, vis con` nected |by a flexible conduit |21 to a source of low pressure air, and at its lower end, beneath the piston, it is connected by a flexible conduit to the valve |24 by which it may be supplied with high pressure air.

With the door I6 closed, the winding of the valve |24 is energized and the winding of valve |23 is deenergized to maintain the former closed and the latter open, connecting the conduit |28 to the atmosphere and permitting the low pressure air to maintain the plunger depressed and the plate |I5 in its downward position clear of the throat of the chute 25. However. when the foot treadle is depressed to open the door kMi the switch |25 on the floor of the munie |0 but I prefer to employ a conveyor, shown as' comprising a series of inverted U-shaped plates |09 adapted to rest on the oor of the mullle. VThe rear plate ||0 has a rod secured thereto which is adaptedy to extend through a suitable slot in the furnace door I6.

The quenching chute 25 adjacent its upper end is provided at the rear thereof with an angular extension ||2, bridged by als solid concave plate I3 and having a pair of convex rails ||4 extending thereacross. Pvoted at the juncture of the upper end of the chute 25 and the forward end of the muflle extension I5 is a plate ||5 which normally extends downwardly against the forward wall of the chute 25, as shown inv dotted lines. This plate is secured to a shaft ||6 extending externally of the chute where it is provided with an operating arm ||1 pivoted to the upper end of a plunge rod ||0 having a plunger ||r9 working within a cylinder |2| mounted on a pivot |22. The plunger is adapted to be operated pneumatically to move the vplate ||5 from the position shown in dotted lines in Fig. l to the horizontal position shown in full lines so as to bridge the upper end of the chute 25. 'I'he free end of the plate ||5 is cut away adjacent each of the rails ||4 to provide finger portions extending therebetween. It is controlled by means of suitable electric valves |23 and |24 op- .raise the same againstthe opposing force is drawn thus pulling the conveyor elements to the throat |02 connected to the gas line closes-energizing the valve |23 to close the same, and the switch |26 is opened to deenergize and open the valve |24, thus permitting the high pressure air to enter beneath the plungerV I0 to of the low pressure air, thereby to move the plate ||5 `to its upward or horizontal position so as to bridge the throat of the chute 25. In this position of the plate ||5, the conveyor elements |00 may be withdrawn to the forward end of the furnace adjacent the door for loading. After they have been loaded and positioned within the muille I0, the door I6 may be closed by the upward movement of the pedal |1. 'I'he switches to its vertical. position adjacent the front wall of the chute 25. When thecarburizing or heat treating operation has been completed the rod forward, with the door I6 closed,

of the chute 25 down which they then travel by gravity, permitting Vthe treated parts thereonA to be dumped one after the other through the chute 25 and into the quenching bath 26. The conveyor may be advanced to the throat of the quench `chute at such rate, depending on the nature of the load and the rate of circulation of the quenching medium in the quench tank, as to keep'the parts suiliciently separated to enable the oil to overheating at the base of the chute, whereby an even quench and uniform hardness is obtained. The atmosphere for the muffle |0 is exhausted through the vent |29 which extends from a point adjacent the lower end of the quenching chute 25, upwardly to above the levelof the munie and as it escapes into theopen air, it is ignited by means of a pilot burner |0| having a conduit It will be noted, therefore; that after the parts have been loaded in the furnace and the door closed, they are continuously subjected to the atmosphere introduced Athrough the conduit |00 into the muille |0 until they enter the quenching bath.

The quench chute 25,

part thereby. To provide additional support while permitting the forward expansion of the munie, a bracket |30 (Figs. l vand 8) is mounted on the forward wall of the furnace. Carried by the bracket |30 is a transverse plate |3| having two bolts Y|32 threaded therein and locked in place by nuts |33.v .-f-The head |34 of the boltsfz|32 are machined The valve |23 provides. a connection from the conduit. |`28 to atmosphere..

absorb the heat therefrom without local as stated, is secured to vthe forward end of the muflle and is supported in ilat and adjusted into engagement .munie I is very small.

l vide sufficient rigidity to give the required support to the chute 25but are `also sumciently resilient to prevent binding Vof the munie in the front wall of the furnace.

In the operation of the furnace the cup |08 con- 'taining the desired lithium compounds is inserted within the pot 91 and the burners in the various chambers I2, 38 and 38 ignited. When the cracking chamber 42 comes up to the required temperature, preferably around"1900 F., an air and gas mixture is introduced therein through the conduit 43. As stated heretofore, in

casevr a heat treating atmosphere is desired, this mixture may be an ordinary combustible mixture of -air and natural or manufactured gas. I prefer to employ a gas such as propane in the cracking chamber due to its uniformity vand in suchv case the mixture may consist of approxima .-iy eighteen' parts air to one part propane. Wh n a carburizing atmosphere is desired, this mixture `.asa-4.00:: l

Thev hydrochloric acid so -formed then reacts'with the lithium carbonate orany lithium oxide in the cup to produce additional lithium chloride as follows:

The lithium chloride formed bythe above conversion reacts with hydrogen, as set forth above,

may be reduced to from ve to ten parts air and one part propane. The gases are cracked within the chamber and as stated pass'through the condenser 81 where the temperature is reduced and the major portion of the water and heavy tars are removed from the gas. The gas is then passed into the pot 91 which is heated to a sufcient temperature by means of the burners 28.

to vaporizea portion of thellithium compound" within the cup |08. Thisvapor is picked up by the incoming gas and carried by it into the mul'lle |0 in which the work is placed.

'I'he preferred charge within the 'cup |08 comprises a mixture of lithium carbonate and lithium chloride in the proportionof about 60% of the former and 40% of the latter, by weight, which has been fused together at a temperature of about 1800 F. With a fused mixture of these proportions, suicient vaporization occurs at a temperature of about 1400 F. to create the desired atmosphere in the muille. The amount of lithium saltv required to produce a non-oxidizing and non-decarburizing and non-staining atmosphere in the With a muille heated to 1400 F. and having a volume of approximately 20,000 cubic inches and provided with a mixture of air and gas entering the gas generator at the rate of about 500 cubic feet per hour, a six ounce charge of lithium salts composed of 40% lithium to liberate a vapor of lithium metal.

In this manner the lithium lcarbonate is gradually converted to the chloride and thus to the metal as the process proceeds. The proportion of 40% lithium chloride and 60% lithium carbonate appears to be so balanced as to render the rate 'of conversion substantially proportional to the rate of dissipation of the lithium vapor into the furnace atmosphere, whereby the liberation of lithium vapor continues at a 4substantially uniform rate until the charge in the cup is .almost entirely consumed. The material leaving the charge in the cup |08 and entrained by the com-- bustion gas thusfappears to `be the vapor of lithium 'metal with possibly' some lithium oxide. The lithium oxide if any, reacts with lthe carbon monoxide in the carrier gases to liberate -lithium metal in accordance with the equation:

2Li2o+co=mco3+2m n The lithium is thus freed to combine with any oxygen inthe furnace from whatever source, and

the lithium carbonate of the above reaction is again brolrenA down thermally within the furnace to lithiumr oxide liberating carbon dioxide or by reactionwith hydrochloric acid gas to lithiumof either reducing any water vapor which so chloride and lithium carbonate, heated in the vapori/zer to a temperature of 1500 F., will supply Asufficient lithium to the atmosphere ,within the muiiie to maintain the same for a period of thirty hours or morein a condition which is neutral to steel so that neither oxidation, nor de-f Y carburization, nor staining thereof will occur. While it is desirable to maintain the charge in the vaporizing chamber at a temperature of at least 1500 F. for the salt mixture specined, the' muille- |0 may be operated at temperatures ranging from 600 F. up to the maximum temperature that the niuille will withstand.

' While the exact nature of the chemical reactions occurring in the charge in the cup |08 or betweenthe generated vapors and the gases from the cracking unit 42 is not fully known, the following explanation is supported by a -large amount of experimental evidence.

The lithium chloride within the cup at the forms at the instant of formation or precludes the formation thereof by interaction withthe oxygen before-it has, arf4 opportunity to combine with the hydrogen to form water vapor. Due to the much smaller amount of water vapor which is formed by reaction within the muille or within the conduits leading Athereto as compared with the amount which would be present in the absence of the condensing apparatus, the amount of lithium required to reduce or prohibit the formation of such water vaporis extremely small. l

.This is true both when employing a heat treating mixture and a carburlzing mixture within the muilie. In both cases y the parte treated are neither oxidized, Vdiscolored, or stained in any manner by the atmosphere and come out of the furnace ina bright and clean condition.

The lithium in addition to protecting the parts from oxidation or decarburizatlon in the case of the heat treating atmosphere,. also serves in the case of. the carburizingatmosphere to accelerate carburization to suchan extent that oxide so peratures.

penetration of carbide is obtained with a much less concentrated hydrocarbon atmosphere than heretofore. For instance, in ordinary gas carburization employing hydrocarbon gases such as propane, it is the practice to employ approximately one part of propane to` two parts of air in order to obtain carburization at a rate which is sufficiently fast to render the process commercially practical. Mixtures of such concentration, however, are sooty in nature and deposit large quantities of carbon or soot upon the parts forming hard carbon scales thereon. As previously stated, applicant is enabled to employ a mixture f one part propane to from five to ten parts of air, which dilution produces a mixture which is substantially completely free of soot. The rate of carburization at such dilutions is much higher than that which is obtained with the ordinary carburizing mixture of two parts air to one part propane, and is of the order of .02 inch for the first hour and .01 inch for each succeeding hour at temperatures ranging from 1650" F. to 1700 F. Rapid carburization, at the ratio of gas and air specified, is also obtained at temperatures as low as 1500* F. This rapid carburization and effectiveness of.the atmosphere at low tempera- 4 intermediate the lugs |40. 4 pedestals |43 from theaftermost to the foremost tures is believed to result from the .fact that the surface is maintained in a clean condition at all times during the carburizing process, and the oxidizing and deoxidizing phase of the usual carburizingl equilibrium is eliminated. The ability` to carburize at a rapid rate at temperatures bei' tween 1500" F. and 1600 F. is of considerable importance because steel in certain shapes tends to distort during carburization at higher tem- While I have referred to propane as the preferred carrier gas, it is to be understood that any type of carburizing gas may be employed.

-It is to be understood that the furnace disclosed may be employed for either carburizing or heat treating merely by changing the proportion of air to hydrocarbon gas introduced into the cracking chamber 42. In case of -heat treating furnaces alone, the cracking chamber 42 is not necessary since the composite gas mixture may bev burned directly in the chamber 39 and exhausted therefrom into the muiiie through the drying and cleaning apparatus 81. l

It will be noted that Athe atmosphere producing unit comprising the control valves 14, 16, pump 11, cracking chamber 42, condenser 61, and vaporizing chamber 38,v have no operative connection with the furnace comprising the mufile |||V and the heating meansy therefor, except the slip connection of the inlet conduit |06 with the rear of the muiiie. Consequently the atmosphere producing unit may be made as a separate unit and employed with any suitable type of muiile furnace or otherwise as desired. It will also be understood that any suitable means may be pro- 'vided for the purpose of preventing admission of-airjinto the mule during the time the door I6 is open, as for loading, etc. For instancethe branch conduits 1| and 12 may be provided with V apertured plates 83 and 84 of such capacity as to provide a sufficient flow of gas through the muille at all times to preclude admission of air thereto during opening of the door, or the admissionl of air into the muflle may be prevented by the provision of a flame curtain adjacent the door opening, or by a chain curtain or other suitablev vmeans.

In Fig. 9 I have shown a modified construction of .the mufile and quenching chute which is particularly adapted for long muilles. In this form the underside of themuiile I0' is provided with a series of lugs |40 recessed to receive the trunnions of a series of rollers |4| which loosely ride thereinpThe rollers |4| rest upon flat plates |42 formed on the top of a series of pedestals |43 whereby the muiiie is supported throughout its length at spaced intervals. If desired, reinforcing ribs |44 may be provided on the mufile The spacing of the In order to obtain a more uniform distribution of the gaseous atmosphere, particularly when the:

furnace is used for carburization, the mufileis provided with a semicircular ridge |45 along its upper side into which isV secured, as by Welding a pipe |46 having a series of slots or other openings |41 spaced along the bottom thereof. The pipe |46 is connected with the outlet of the lithium vaporizer, that is to the conduit |06 of- Fig. 1, and the lithiated atmosphere produced therein enters the muflle through the openings |41. These openings are of increasing width from the after end to the forward end of the pipe so that the amount of atmosphere admitted to the muiiie at each point will be substantially constant despite the decrease in pressure toward the forward end of the pipe |46. This introduction of the'gas at spaced points along the muie is important in the carburizing of certain shaped parts, since when the atmosphere is introduced only lat the rear of the muiiie, the flow of the gas through the muiiie tends to produce an air flow effect on one side thereof which causes a reduced gas pressure on such side and causes a slight unevenness in the carburization. There yis also a tendency toward a stagnation of the gas in vertical openings in the kparts being car-` burized. This difficulty is entirely obviated with.

the overhead introduction of the gases since this causes a downward and turbulent flow of the gases in addition to the longitudinal movement thereof.

In the muille of Fig. 9 I have shown a modified form of work conveying belt |09', this being in the form of a. woven or mesh belt having a series of upstanding pivoted links along the sides thereof to form a trough. The belt is free at the forward end` and is secured to a rod at its rear end. The quench chute 25 is provided with the same throat member H5 described in connection with Fig. 1, across which the belt may be drawn through the door opening to enable the belt to be loaded with parts to be treated After completion of the treatment, the rod III' is drawn forward, with the door closed so that the throat member H5 occupies the vertical position against the front wall of the quench chute 25'.

During this movement of Athe belt, theiorward end thereof drops into the chute 25' by gravity, following the curved rails H4 and entering between the rails ||4 and arcuate guide lingers |48, whereby the free end of the belt is directedquench tank 2,6. During the forward movementv of the belt it accumulates in the chamber |49 and is thus protected-from engagement with the quenching medium in the quench tank 26, which 4 medium`if permitted t0 contact the belt might deteriorate and dirty the same.

In o rder to produce a thorough circulation of the oil withinthe quench tank 26 there is shown in Fig. 11 a pair of circulating propellers |5I, |52

' disposed with their blades interleaved and driven froma common motor |53 :through a sprocket drive |54. The shafts |55 and |56 of Ithe blades rotate in suitable bearings |51 carried by brackets secured to the outer-.wall of the tank 26. The

drive'shaftV |56 is.driven at a reduced speed,

preferably around 400 R. P. M., from the motor |53 by a suitable belt |58. In orderto prevent stagnation of the oil within the lower end .of the quench chute 25 I provide a deflecting plate |59 on one sidethereof away from the blades 5| and |52, which causesna deflection and circulation of oil up into the lower end of the quench chute. This is essential in order that the oil will be in movement at the moment of contact withthe piece being quenched,since the forma- 4tion orf-,oil vapor bubbles in the quench chute, which occurs with stagnant oil, prevents proper contact of the parts with the quenching medium.

-In' the base of the quench tank is a mesh basket or receptacle |6| into which receives .the parts dropped through the chute 25. This receptacle is also providedv witha deflecting plate |62 to prevvent stagnation ofthe oil therein. The basket clockwise direction and the coil |61 to drive the shaft in a counter-clockwise direction. A second Jshaft |10, driven by the shaft |65 through reduction gearing |1|, is journaled in bearings |12.

and extends axially through a, fixed disc |13 having suitable graduations thereon. The outer end of the shaft |10 carries contact armv |14 ladapted to engage either of two adjustable con- |85. A pair of spaced contacts are provided at? each end of the switches |84, |85, the right hand` contacts Aof switch |84 controlling the field winding |66 and the left hand contacts thereof controlling the field winding |61, to drive the motor either clockwise or counterclockwise depending upon the position of the switch |84. The right hand contacts of switch |85 are connected through a manual switch |86 to the windings ofl Y the electric gas and air valves 14h, 16h, or 14c.,

16o (Fig. 1), depending upon the position'of the switch |86. 'I'he left hand contacts of switch |85 control the operation of thefgas and air valves v 14aand 10d.

rests upon suitable runners '|60 by which it may l be drawn forward of the. quench chute for removal, when required. In shallow tanks where the basket-IBI is relatively close to the lower end of the quench chute, a single circulating blade is sufiicient, but in orderto provide a greater oil Assuming that the furnacehas been brought up to heatand it is desired to alternate a carburizing and a diffusing cycle, the switch |86 is- .operated to either its lower or upper contact depending upon the concentration of case desired in the steel to-be carburized. The contact |15 is adjusted in contact with the arm |14 of the capacity where a large quantity of parts are to.

b e quenched, I prefer to employ a deep tank and I to use the two blades as shown in Fig. 11,v one approximately at the level of the lower end of the chute and the other approximately at the levelofl the top of the basket. By disposing the upper blades so as to interleave with the lower blades, and maintaining this relation by a sprocket drive, a substantially continuous move-f ment of the oil is maintained and pulsations in the flow thereof eliminated. A pair of inclined side plates |63 extend inwardly and downwardly from opposite sides ofthe tank 26 to overhang. the side edges of the basket and direct the work intov the same. As heretofore stated, it is at times desirable to valternate the carburizing cycle and the heating cycle in order that the carbides absorbed during the'carburizing cycle may be more uniformly diffused into the steel during the heat treating cycle. For instar ce, it may be desired to operate the furnace with a carburizing atmosphere for aperiod of thirty minutes and then change to a neutral atmosphere for a further period of thirty minutes to permit diusion ofthe carbides, and

to repeat these cycles a number of times, depending upon the depth of the case desired. VIn Fig. 1 2 I have shown an automatic timing mechanism for effecting such control .of the furnace atmosphere. The timing mechanism comprises a reversing self-starting alternating' currentl synchronous motor |64, comprising a shaft |00 journaled in suitable bearings and having a pair of field windings |60 and |01 on iron cores |08 and |69, respectively,. adapted. to'operate` 'the -mowr in opposite directions when energized. The coil |00 iaarranged to drive the shaft in-a timing mechanism and the contact |10 is spaced therefrom a distance corresponding to the length ofthe carburizing cycle, as indicated by the graduations on the disc |13. The line switch |81 is then closed to complete a circuit from the B bus bar through the brush |80, shaft |10, arm |14,l

and contact |15, to the winding |8I of the control relay and thus to the A bus bar. The armature |83 is thus pivoted clockwise to the position shown whereby the right hand contacts of each of the mercury switches |84, |85 are bridged. The clockwise operating winding |66 of the driving motoris thus energized from the B bus bar and right hand contacts of switch |84 to the A bus bar, causing the shaft |05 to'rotate clockwise and to thus start the travel of the arm |14 towards the upper contact |16. At the same timefa circuit yis completed from the B bus bar, through the right hand contacts of switch |85, and through switch |86 to the selected pair of gas and air valves 14h, 16h, or 14e, 16c. The control relay is of the type that remains in its last set position,

so that the right hand terminals ofthe mercury switch remain bridged until the winding |82 of i the relay is energized to reverse the position of the armature. This occurs at the time the ,contactarm. 14 engages contact |10 and the elapsed period required for the arm |14 to travel from contact |15 to contact, |16 determines the length of the carburizing cycle'. Upon closureA of the circuit through the/contact |10, the winding |02. of the control relay is'energized, rreversing the position of the armature and thereby opening the'right hand contacts of the mercury switches v and closing the left hand contacts. The lefthand contacts of the switch |84 energize the held winding |01 of the driving motor to reverse .the direcingaheating of atmosphere into said vaporizing chamber,

condensing means tion thereof and start the movement of the switch arm ill back towards the contact |15. The left hand contacts of the switch |85 energize the electric valves 1,4a and 16a to change the ratio'of gas and air admitted to the furnace whereby a neutral atmosphere is substituted for the carburizing l atmosphere previously employed. This condition 1. A furnace comprising a heating chamber, a

` vaporlzing chambe means within said vaporizing chamberfor supporting a receptacle adapted to hold a vaporizable material, a removable closure for said vaporizing chamber- 4for the insertion andremoval of said receptacle, means for heating said vaporizing chamber to a suiilcient temperature to' effect vaporization of said material at an appreciable rate, means for supplying a gaseous-medium to said vaporizing chamber and means for conducting said gaseous medium from said vaporizing chamber into said heating 2. A furnace for the treating of metal comprischamber for such metal, a vaporising chamber, a removable container for vaporisable-material adapted to be supported in the base of said vaporizing chamber, ra conduit extending from said vaporizing chamber into said heating chamber, a source of atmosphere for said heating chamber, a conduit 'extending from said source vaporizing chambe and baille meansin said vaporizing chamber in the path o'f said atmosphere, said baille means extending adjacent to but spaced above' said removablecontainer intermediate said conduits.

3.V A furnace for the treating of metal comprising a heating chamber for such metal, a vaporizing chamber. a removablecontainer for vaporizabie materiall adapted to be supported in said' a conduit extending from said vaporizing chamber into said heating chamber, a gas generating chamber, a conduit extending from said gas generatingchamber into said vaporizing chamber, and means for introducing:

fuel and air into said gas generating chamber for reaction therein.

a vaporizing chamber, a plurality departing v teria! as to enable tially all water from said reacted gases entering said heating chamber to be eifected.

5. A furnace for the treating of metal comprising a heating chamber for such metal, a. vaporizing chamber, a removable container for vapory izable material adapted to be supported in said vaporizing chamber, a conduit extending from said vaporizing chamber into said heating chamber, a gas generating chamber, a conduit'extending from said gas generating chamber into said mixing devices, andmeans for operatively associating any one of said gas and air mixing devices with said gas generating chamber for supplying a gas and air mixture thereto.

8. A furnace for the heat treating of metals comprising a muille,.a combustion chamber surrounding combustion chamber surrounding said vaporizng receptacle, a conduit extending from said vaporizing receptacle into said muiiie, a gasgenerating chamber, a conduit extending from said gas generating chamber into said vaporinng receptacle,

' Aburners extending into each of said chambers,

means for supplying air and fuel gas to said burners, and means for varying the air and fuel gas supplied to each of said chambers independently.

7. A furnace for the heating of metals comprising a munie, a closed co bustion chamber surrounding said munie, said combustion chamber having means for supplying a` combustible mixture supplying a' combustible confining a vaporizable material within tl'e porchamber to said muiile,

A4. A furnace for the treating of metal comprising a heating chamber for such-metal, a vaporizing chamber,

heating chamber,

v extending from said gas, generating chamber into said vaporizing means for introducing fuel and air into said gas generating chamber for reaction therein, and water;

tioned conduit for removing a of the water from said reacted gases, the capacity of said water condensing means being suchrelative to the' vapcrizing capacity of. said vaporiaing chamber for said water reducing inaa 'removable container for vaporv Said meins permitting associated with said last mencondensing carbonaceousgas thereto and for exhausting the bustion therefrom, a second closed combustion chamber, means for introducing a carbonaceous "gas and air mixture into said second combustion chamber, an exhaust conduit extendingfrom said second combustion chamber into one end of said muiile, a third closed combustion chamber disposed about a portion of said conduit, means for l into said third combustion chamber and means for exhausting the products of combustion therefrom, means for from said second combustion muille disposed at the opposite end thereof from said conduit, a door normally closing said muiile andfmeans for operating said door to permitthe introduction and removal of material to be heated into and from said munie.

Y 8. A furnace for the heating of metals comprising a muiiie, means `for heating said munie, a

' gas 'generatingchamben means for introducing a mixture into'said gas and airgenerating'chamber for reaction therein, an exhaust conduit extending from said gas generating chamber into saidv muine. heating means for a portion of said conduit, means for connning a vapor'izable material within the portion of said conmoval of material to be munie.

9. A furnace for the heating of metals comprisinga munie, means for heating gas generating chamber, means for introducing a carbonaceous gas/and air mixture into said gas for reaction'therein, an exhaust conduit extending from the summation of substanl of `gas and air y said muiile, a vaporizing receptacle, a

products cf coman exhaust outlet for-said v inthe path said munie. a 4

said ses generating 1 chamber into said muiile, heating means for a portion of said conduit, a recess in the portion of said conduit subject to said heating means and in the path of the exhaust gases passing from said gas generating chamber to said muiiie, a removable closure for said conduit adjacent said recess and an exhaust outlet for said muiile to permit vthe egress of the muiile atmosphere.

10. In a metallurgical furnace, the combination of a heating chamber, a gas generating chamber, a vaporizing chamber, passageways extending from said gas generating chamber to said vaporizing chamber and from said vaporizing chamber to said heating chamber, heating means for each of said chambers, means for supplying a mixture of gas and air to said gas generating chamber and means for varying the ratio of said gas and air mixture.

11. In a metallurgical furnace, the combination of a heating chamber, a gas generating chamber, a vaporizing chamber, a gas drying chamber, passageways extending from said gas generating chamber to said drying chamber, from said drying chamber to said vaporizing chamber and from said vaporizing chamber to said heating chamber, heating means for each of said heating, gas generating and vaporizing chambers, means for supplying a mixture of gas and air to said gas genlatter passageway having a plurality of outlets within said mufile.

17. In a metallurgical furnace, the combination of a mulile, a gas generating chamber, a vaporizing chamber;heating means for each of said chambers, means for introducing a gas and air mixture into said generating chamber, a passageway from said generating chamber to said vaporizing chamber, a passageway from said Vaporizing chamber to'said mule, said latter passageway lhaving a plurality of outlets within said muflle disposed at spaced points therealong.

erating chamber and means for varying the ratio ofv said gas and airmixture. v

12. In a metallurgical furnace, the combination of a heating chamber, a gas generating chamber` a vaporizing chamber, passageways extending from said gas generating chamber to said Vaporizing chamber and from said vaporizing chamber to said heating chamber, heating means for each of said chambers. means including a pump for supplying a mixture of gas and air to said gasv generating chamber and means for varying the ratio of said aas and air mixture. 1

13. In a metallurgical furnace, the combination of a heating chamber, a gas generating chamber, a vaporizing chamber. passageways extending from said gas generating chamber to said vaporizing chamber and from said vanorizing chamber to said heating` chamber. heating vmeans for each o'f said chambers, a gas and air mixing device having separate air and gas inlets and metering means in each of said inlets for supplying a mix- :gre of gas and air to said gas generating cham- 14. In a metallurgical furnace, the combinationof a heating chamber, agas generating means, a vanorizing means, means for passing gas from said gas generating means to said vaporizing means and thence to said heating chamber, means for supplying a mixtureof gas and air to said gas generating means, means for varyina the ratio of said gas and air mixture, and

timing means for altering the ratio of gas and air at predetermined intervals.

15. In a metallurgical furnace, the combinavtion of a'heating chamber. a gas generating chamber. a vaporizing chamber, passageways extending from said gas generating chamber to said vaporizing chamber and from said vaporizng lchain-ber to said heating chamber, and a plurality of separate means for supplying mixtures o1' gas and air of diierent proportions tosaid gas generating chamber. Y

16. In a metallurgical furnace, the combina.-

tion of a muftle, a source of gas, a vaporizingl chamber, a passageway from lsaid source of gas to said vaporizing chamber, and a passageway from said vaporizing chamber to said muiiie, said 18. A generating unit for metallurgical furnaces comprising a gas generator, a vaporizing chamber having inlet and outlet passageways, a conduit extending from said gas generator to said inlet passageway whereby gases produced in said generator may iiow through said vaporlzing chamber, means for retaining a vaporizable material in a portion of said vaporizing chamber disposed to Vone side of the path of iiow of-said gases through said chamber and means for heating said portion of said vaporizing chamber.

19. A generating unit for metallurgicalfurnaces comprising a gas generator, a vaporizing chamber having inlet and outlet passageways, a conduit extending from said gas generator to said inlet passageway whereby gases produced in said generator may flow through said vaporizing chamber, means associated with said conduit for extracting at least a part of the water contained in said gases, means for retaining a vaporizable material in a portion of said vaporizing chamber disposed to one side of the path of ow of said gases through said chamber and means for heating said portion of said vaporizing chamber.

20. A gas generating unit for metallurgical furnaces comprising a gas generating chamber, a vaporizing chamber, a passageway extending from said gas generating chamber to said vaporizing chamber and from said vaporizing cham- .berto said heating chamber, heating means for 2l. A gas generating unit for metallurgical fur,-l

naces comprising a gas generating chamber a vaporizing chamber, a passageway extending from said gas generating chamber to said vaporizing chamber and from said vaporizing chamber to said heating chamber, means including a pump for supplying a mixture of gas and air to said gasgenerating chamber and means for varying the ratio of said gas and air mixture.

22. A furnace comprising a heating chamber, a vaporizing chamber communicating with said heating chamber, means for introducing a vaporizable material into said vaporizing chamber, means for heating said vaporizing chamber to a sufficient temperature to eifect vaporization of said material -at an appreciable rate,and means for passing a gaseous medium through'said'vaporizing chamber.

23. In a metallurgical furnace, the combination of a heating chamber, a vaporizing chamber,

means for introducing a vaporizable material into said vaporizing chamber, means for' heating said vaporizing chamber, an inlet conduit for said vaporizing chamber for admitting a gaseous medium thereink and an outlet conduit for removing said gaseous medium therefrom, said outlet conduit communicating with said heating chamber at a plurality of spaced points therein.

24, A furnace for the treating of metals coma gaseous medium through said vaporizing champrising a heating chamber for such metal, a vaber and linto said heating chamber and baflie porizing chamber communicating with said heatmeans in said vaporizing chamber in the path of ing chamber, a removable container for the vasaid gaseous medium for deecting same into porizable material adapted to be supported in 5 contact with said vaporzable material. l said vaporizing chamber," a. source of atmosphere HAROLD J. NES. for said vaporizing chamber. means for directing a 

